April 4, 2011 -- Breast milk may someday do more than help babies thrive. It may help determine a woman's risk for developing breast cancer.

Preliminary findings from an ongoing study suggest that cells found in breast milk may identify women who might go on to develop breast cancer.

The findings were presented Monday in Orlando, Fla. at the annual meeting of the American Association for Cancer Research.

The study expands on a growing area of cancer research involving DNA methylation patterns.

DNA methylation is one of several mechanisms involved in gene expression. Previous studies have shown that methylation patterns are dramatically altered in cancer and even in people who have not yet developed the disease.

But the study of methylation in breast cancer has previously been limited to cells obtained using invasive methods such as injecting a needle or catheter into the nipple.

Looking for Clues on Breast Cancer Risk

In the newly reported study, researchers from the University of Massachusetts wanted to find out if breast milk obtained from lactating women held useful information about breast cancer risk.

Study researcher Kathleen F. Arcaro, PhD, examined breast milk samples provided by close to 250 lactating women considered to be at high risk for breast cancer because they had had a breast biopsy or were scheduled to have one.

Most women who submitted milk samples were enrolled in the Love/Avon Army of Women project, which registers women willing to participate in breast cancer research.

The women submitted milk samples from both breasts, which were processed within 24 hours of being expressed. The researchers looked for potentially cancerous cells, known as epithelial cells, from the breast milk and then isolated DNA from these cells.

Genetic Search

The researchers looked for the presence of three of the more than 30 genes known to be associated with methylation in breast cancer.

Cancer was confirmed in 13 of 182 women with complete biopsy reports, Arcaro said Monday at a news briefing.

These women showed significantly more methylation of one of the methylation-associated genes in the biopsied vs. non-biopsied breast.

While the sample size was small, Arcaro says the findings indicate that breast milk can provide meaningful information about breast cancer risk.

The study is ongoing and researchers plan to analyze nine other genes associated with methylation in breast cancer, as well as collect and analyze samples from more women having biopsies.

The hope, Arcaro says, is that the technique can be used to screen new mothers to determine if they are at increased risk of developing breast cancer in the years to come.

Johns Hopkins oncology professor David Sidransky, MD, says scientists, clinicians, and the public have begun to understand the importance of finding better ways to identify people at risk for cancer.

"Efforts to treat and cure cancer have focused on turning the tables in patients with advanced disease," he says. "Even the greatest successes have been moderate at best because once cancer is advanced it is very difficult to treat."